To define the mean effective dose of oral misoprostol, a PGE2 methylanalogue, for terminating midtrimester complicated pregnancy without producing significant side-effects and complications, forty-two patients with intrauterine complicated pregnancies of 14-28 weeks were treated with oral misoprostol. All patients were observed after the initial dose (200 micrograms). If there was no contraction of the uterus or no vaginal bleeding, a supplementary dose of 200 micrograms misoprostol was given once each hour, with an average total dose of 1000 micrograms being given (min. 200 micrograms, max. 1200 micrograms). Abortion was successfully induced in 39 women (92.9%); there were 3 failures (7.1%). The mean time from initial dose to abortion was 9 h. No important side-effects or complications were noted. This study demonstrated that the use of oral misoprostol is a simple, inexpensive and easy procedure for termination of second trimester complicated pregnancy.